The process described herein is applicable to the conversion of petroleum crude oil residuals having high metal content and an asphaltene fraction. More specifically, our invention is directed toward a method for effecting a catalytic slurry process, in the presence of hydrogen, in order to convert hydrocarbonaceous feedstocks, such as, atmospheric tower bottoms, vacuum column bottoms, crude oil residuals, topped and/or reduced crude oils, coal oil extracts, shale oils, deasphalter pitch, crude oils extracted from tar sands, etc., all of which are commonly referred to in the art as "black oil."
Petroleum crude oils, and particularly the heavy residuals derived therefrom, contain sulfurous compounds in exceedingly large quantities, nitrogenous compounds, high molecular weight organometallic complexes principally comprising nickel and vanadium as the metallic component and asphaltenic material. The latter is generally found to be complexed with sulfur, and, to a certain extent, with the metallic contaminants. A black oil is generally characterized in petroleum technology as a heavy hydrocarbonaceous material of which more than about 10 volume percent boils above a temperature of about 1,050.degree. F. (referred to as nondistillables) and which further has a gravity generally less than about 20.0.degree. API. Sulfur concentrations are usually high, most often in the range of about 2 to about 6 weight percent. Conradson carbon residual factors exceed 1.0 percent by weight and the concentration of metals can range from as low as about 10 ppm to as high as about 2000 ppm by weight or more.
The process encompassed by the present invention is particularly directed toward the conversion of those black oils contaminated by large quantities of asphaltenes and having a high metals content--i.e. containing more than about 10 ppm by weight. Specific examples of the charge stocks to which our invention is adaptable include a vacuum tower bottoms product having a gravity of 7.1.degree. API and containing 4.1 percent by weight of sulfur and 23.7 percent by weight of heptane-insoluble materials; a "topped" Middle-East crude oil having a gravity of 11.0.degree. API and containing about 10.1 percent by weight of asphaltenes and 5.2 percent by weight of sulfur; and, a vacuum residuum having a gravity of 8.8.degree. API, containing 3.0 percent by weight of sulfur and 4,300 ppm by weight of nitrogen.
Candor compels recognition of the fact that many slurry-type processes have been proposed for the catalytic conversion of hydrocarbons. Regardless of the various operating and processing techniques, the principal areas which have confronted those skilled in the art include the separation of the effluent to provide substantially catalyst-free distillable product, the uninterrupted catalyst recirculation, and the continuous, smooth, unimpeded flow of the reactants and the slurry catalyst through the entire process and particularly in the reaction zone.
U.S. Pat. No. 3,622,498 (Stolfa et al), incorporated herein by reference, is a representative example of the prior art teachings in the area of slurry catalyst processing of heavy hydrocarbonaceous oil. The Stolfa et al patent teaches that an asphaltene-containing hydrocarbonaceous charge stock may be converted by forming a reactive slurry of the asphaltene-containing hydrocarbonaceous charge stock, hydrogen and a finely divided catalyst containing at least one metal component from the metals of Group V-B, VI-B or VIII; and reacting the resulting slurry in a reaction chamber at conditions including a pressure above about 1,000 psig and a temperature above about 800.degree. F.
Those skilled in the art of hydrocarbon processing have not recognized that under certain conditions which are commonly encountered in slurry catalyst processing of asphaltene-containing hydrocarbons, that the reaction zone may contain foam which reduces the efficiency of the slurry conversion process. Since the foaming problem in the reaction zone of a slurry catalyst process has not previously been known to the art, the solution to the problem, of course, has also not been known. We have discovered that foaming is a significant problem in the slurry conversion process and that the efficiency of a catalyst slurry process is enhanced when the amount of foam is minimized, thereby enabling full utilization of the reaction zone. The black oil typically utilized in a slurry catalyst process is particularly susceptible to the formation of foam when subjected to the necessary hydrocarbon conversion conditions. The present invention achieves the full utilization of the reaction zone by the addition of antifoamant as hereinafter described, thereby reducing any foaming tendency and thereby improving process stability and efficiency.